Crystal could have redeem the four sisters

The Shitennou's redemption was poorly done in Crystal, so why repeat the same bad mistake? There is no way they could fit in a redemption arc for the Ayakashi Sisters in a season that was already crammed due to a 1:1 adaptation style.

And yes the Ayakashi Sister's redemption was one of the better arcs of the '90s anime, but their characters were completely different. For example, '90s anime Koan was never shown burning people to death.

The redemption wasn't really bad, the romance with the Inner was.

I think they could let the sisters get injured but not killed in their operation, then show up realize they have been used by Wiseman and defect/redeem themselves like Demande did to buy some time for Usagi.

It's possible to remove Koan's killing just like Crystal didn't let Demande kill the girl like he did in the manga.

What you're describing sounds like terrible writing. All four of them defecting would be contrived and you would need time to establish their motives, backstories because all of them suddenly having a change of heart just doesn't make any sense. The original anime had the time to make these characters sympathetic. The manga did not.

You're wanting Crystal to simply change the story to fit your own tastes rather than looking at what even makes sense in the narrative.

I don't see it so hard since Wiseman was using them and killed Rebeus for that, even tried to brainwash Demande and his brother to serve the purpose. It would require some writing but cost little screen time. In their operation they could also be introduced as softer heart individual who wanted to help their people instead of heartless minions.

You can be used and be a shitty person, these things are not mutually exclusive. And of course it would cost screen time. You not only need to take time to develop them as characters, but will now have to figure out how to add a whole subplot of them defecting and going against Wiseman as you described... All of which is completely unnecessary when they were nothing but Monsters of the Day in the manga whom the '90s anime changed.

If anything, I agree that the Ayakashi Sisters could have had a little more time being fleshed out, but like a quick scene showing them being absolute monsters in Crystal Tokyo... Rather than trying to paint them out to be sympathetic when the manga had no intention of painting them as such.
After all, why does every new Sailor Moon media have to follow what the '90s anime did? That's boring and unimaginative.

But it can also be revealed that BMC were not all made of bad ppl. Also Crystal did spend time on Berthier having chess game showing her manipulation, the same screen time could be used to make her somehow sympathetic.

Yeah the manga has no intention to do that, but if Crystal simply tried to make the characters more likeable it's entirely doable even with current screentime.

Because compare to the manga, the 90s anime made the sisters more like human being instead of monsters of the week with almost 0 characterization. Even the most well developed BMC villain Demande got a rushed ending, which is why many ppl like Crystal's change.

Sure. Why not make ALL of the manga's villains likeable then? Maybe reveal Wiseman is actually a cute old grandpa hidden underneath his robes? Have Pharaoh 90 be redeemed by Sailor Moon's Silver Crystal and have him work part-time at the Hikawa Shrine. Maybe instead of defeating Mistress 9, she could become Hotaru's new imaginary friend that she talks to like Chibi-Usa with Pegasus in the SuperS season. All of this is completely doable in Crystal's limited screen time and who cares about what the manga's original intention for these characters are, right?

(Also Crystal didn't even redeem Demande like you're trying to claim. They added in one moment that tried to paint him in a more sympathetic light, but he died anyway. Hardly a redemption arc. You're making false equivalencies.)

The shitennou were not evil, they were Endymion’s Guardians and they also come back in the Dark Moon arc, just like they do in the manga. Although most people seem to dislike the way Crystal handled the four members, I approve and am completely fine with it. The manga doesn’t reveal that the shitennou were good until the second arc, so I fully approve what Crystal did in season 1.

The four sisters, on the other hand, have no background whatsoever; all that is known is that they blindly follow Rubeu’s orders.

Crystal is a more accurate adaptation of the manga, that includes the four Weird Sisters. Crystal is not a remake of the 90's anime. The Four Weird Sisters' redemption in the 90's anime makes sense, there was build up. Crystal didn't have that build-up.

Yes, the four sisters were “monsters-of-the-day” wearing actual couture gowns. Of all Sailor Moon villains, they are probably the best dressed. Naoko got their outfits from renowned fashion designers.

The shitennou were not evil, they were Endymion’s Guardians and they also come back in the Dark Moon arc, just like they do in the manga. Although most people seem to dislike the way Crystal handled the four members, I approve and am completely fine with it. The manga doesn’t reveal that the shitennou were good until the second arc, so I fully approve what Crystal did in season 1.

The four sisters, on the other hand, have no background whatsoever; all that is known is that they blindly follow Rubeu’s orders.

It's not hard to add some to make them redeemable, such as misguided by Wiseman and recruited into the BMC, just like Another Story's opposite senshi.